Project Summary The goal of this application is to image and identify nuclear lamina-interacting proteins in living cells. The nuclear lamina, located underneath of inner nuclear envelope, is composed of four major homologous proteins, lamin A (LA), lamin B1 (LB1), lamin B2 (LB2) and lamin C (LC). Lamins are type V intermediate filament proteins and provide mechanical support for the mammalian nucleus. However, the roles of lamins have been significant extended into other critical aspects of cell biology including mechanosensing DNA repair, chromatin regulation, gene transcription and stem cell regulation. The function of lamins in these processes are mediated by complex yet incompletely understood protein-protein interactions at the nuclear lamina. The importance of LA in these biological processes is further emphasized by the fact that more than 450 LA mutations are known to cause a wide spectrum of diseases collectively called laminopathies. One of the major obstacles in addressing this challenge is the lack of the appropriate tools and technologies to image and identify the lamina-binding proteins in living cells under physiologically relevant conditions. We recently developed a small molecule called LBL1 that specifically binds lamins in the whole cellular proteome. Our identification of LBL1 provides an unprecedented opportunity for us to image and identify the endogenous lamin-binding proteins in living cells. This understanding will generate novel insights into the lamin functions and potentially provide novel avenues to develop therapies for laminopathies. To achieve this goal, we propose the following two specific aims: 1) To develop an innovative chemical probe to label nuclear lamina in living cells; 2) To identify and image LA and its interacting partners in living cells.